Discovery Communications

Whale Wars The Hidden Life of the Sperm Whale

posted: 05/15/12

DCL

The deep sea life of the sperm whale was, until recently, a mystery. As recently as 2004, scientists were unclear whether the sperm whale was an active hunter or a sit-and-wait predator. Today, we know how sperm whales locate their prey, what they eat, how they're equipped for deep dives and much more.

How Do Sperm Whales Locate Their Prey?

When a sperm whale dives below the surface, it sees by sound rather than sight. It sends out clicks from its massive head.

The clicks originate when air is sucked in through a tight valve near the blowhole. The pulses of air pass through the spermaceti — milky-white, waxy fluid found in the sperm whale's head cavity that acts like an acoustic lens, magnifying the air pulses into clicks.

Sent methodically into the darkness, these clicks allow the sperm whale to echolocate its prey hundreds of meters or up to tens of miles away.

What Do Sperm Whales Eat?

The sperm whale is the deepest diving mammal in the world. A typical dive is 1,300 feet, but the sperm whale can go much further, nearly two miles beneath the surface of the ocean.

The creatures it finds down there are strange variations on those we know in shallower waters. Cephalopods — squid, octopus and cuttlefish — make up the majority of its diet. The sperm whale also hunts the largest invertebrates on earth: the giant and colossal squids, active hunters with deadly tentacles.

The voracious sperm whale needs to eat over a ton of food every day.

How Are Sperm Whales Equipped for Deep Dives?

From its bulbous head to its spade-like flukes, the sperm whale is built for deep sea diving. The flukes, or tail, propel the great animal into the murky depths at a rate of one meter per second.

In a world without sunlight, it uses echolocation to find its way around the deep sea canyons and seamounts, and to locate its prey.

The sperm whale can hold its breath for up to 90 minutes. To conserve oxygen, it decreases its heart rate while redirecting blood to the brain and essential organs. Its flexible ribs allow for its lungs to collapse as water pressure increases; this lets the sperm whale dive even deeper. As it reaches 1,000 meters, where it does most of its hunting, the sperm whale reaches natural buoyancy.

Until recently, some scientists thought the sperm whale stunned its prey with loud clicks, or possibly waited motionless with its mouth open like a deep-sea angler fish. Acoustic tagging in 2004 revealed that the sperm whale is actually an active hunter, prowling its environment in search of prey.

When it surfaces, the sperm whale spouts repeatedly to expel de-oxygenated air. It must rest for at least eight minutes before diving again. Once its blood has been re-oxygenated, the sperm whale arches its back, flicks its massive flukes skyward and dives again.